It is known to employ polycarboxylate type comb polymers as grinding agents for preparations containing cement and cementitious materials, including the grinding of cement clinker and/or pozzolanic materials to produce hydratable Portland cement, blended cements, pozzolanic cements, and other cementitious compositions.
For example, in U.S. Pat. No. 6,641,661, Jardine et al. disclosed the use of polyoxyalkylene-containing comb polymers in combination with sugar and alkali or alkaline earth metal chloride for grinding cements, and particularly for grinding pozzolanic cements. This patent, owned by the common assignee hereof, describes that such comb polymers contain backbone and pendant groups. Preferably, the backbone contains carbon groups to which are attached pendant polycarboxylic acid units, which function to attach to cement particles, as well as pendant “EO/PO” groups that function to control the dispersing properties of the polymer within aqueous cementitious pastes and slurries. The letters “EO/PO” refer to ethylene oxide (EO) and propylene oxide (PO) units typically comprising the polyoxylalkylene repeating groups.
Jardine et al. suggested that water-reducing EO/PO type comb polymers disclosed in U.S. Pat. Nos. 4,946,904, 4,471,100, 5,100,984, and 5,369,198 could be used cement grinding preparations. These involved copolymers made from polycarboxylate monomers such as maleic acid or anhydride and polymerizable EO/PO-containing monomers such as polyalkylene glycol monoallyl ethers. Another exemplary polyoxyalkylene comb polymer was taught in U.S. Pat. No. 5,840,114 wherein the (co)polymer was described as having a carbon containing backbone having attached groups shown by the structures (I) and (II) and optionally groups shown by structures (III) and (IV) as shown below:
wherein each R independently represents a hydrogen atom or a methyl group (—CH3) group; A represents hydrogen atom, a C1-C10 alkyl group, R′ or an alkali metal cation or a mixture thereof; R′ represents a hydrogen atom or a C2-C10 oxyalkylene group represented by (BO)nR″ in which O represents an oxygen atom, B represents a C2-C10 alkylene group, R″ represents a C1-C10 alkyl and n represents an integer of from 1-200, or mixtures thereof; and a, b, c, and d are numerical values representing molar percentage of the polymer's structure such that a is a value of 50-70; the sum of c plus d is at least 2 to a value of (100−a) and is preferably from 3 to 10; and b is not more than [100−(a+c+d)]. (The letter “B” does not, of course, represent boron but is merely intended as a symbol).
In US patent application Ser. No. 095799 (Publ. No. 20080293850), Pakush et al. also disclosed a comb polymer useful as a grinding agent for preparations containing cement. According to the abstract, the comb polymer contains a carbon backbone bearing polyether groups of the formulaA*-U—(C(O))k—X-(Alk-O)n—W Awherein the asterisk “*” indicates the binding site to the carbon backbone of the comb polymer, U stands for a chemical bond or an alkylene group with 1 to 8 C atoms, X means oxygen or a NR group, k is 0 or 1, n stands for a whole number, the mean value whereof, based on the comb polymer, lies in the range from 5 to 300, “Alk” stands for C2-C4 alkylene, where Alk within the group (Alk-O)n can be the same or different, W means a hydrogen, a C1-C6 alkyl residue or an aryl residue or means the group Y—Z, Y stands for a linear or branched alkylene group with 2 to 8 C atoms, which may bear a phenyl ring, Z stands for a 5- to 10-membered nitrogen heterocyclic group bound via the nitrogen, which can have as ring members, as well as the nitrogen atom and as well as carbon atoms, 1, 2 or 3 additional hetero atoms, selected from oxygen, nitrogen and sulfur, wherein the nitrogen ring members can contain a group R′, and wherein 1 or 2 carbon ring members can be present as carbonyl groups, R stands for hydrogen, C1-C4 alkyl or benzyl, and R′ stands for hydrogen, C1-C4 alkyl or benzyl; and functional groups B, which are present in the form of anionic groups at pH>12, and salts thereof as grinding aids in cement-containing preparations.
Pakush et al. also recounted a number of prior art comb polymers used as concrete additives, and described a number of patented comb polymers including the following:
The comb polymers of EP-A 331 308 contain monoethylenically unsaturated carboxylic acid, a monoethylenically unsaturated sulfonic acid, and an ester of a poly-C2-C3 oxyalkylene glycol mono-C1-C3 alkylether which is located in the tip of a pendant group.
The comb polymers of EP-A 560 602 of Koyata et al. contain an ether of a poly-C2-C18 oxyalkylene glycol mono-C1-C4 alkylether and maleic acid or maleic anhydride polymerized together. Koyata et al. describe that the purpose of these comb polymers is to achieve high flowability and resistance to segregation into the concrete in which the polymers are admixed, and these properties are beneficial for general construction uses such as lining of tunnels and pouring for re-bar reinforced concrete structures. However, this reference makes no suggestions regarding how to sustain robustness of polymeric structure necessary for surviving milling of cementitious materials as in the present invention.
The comb polymers of EP-A 753 488 contain mono-ethylenically unsaturated carboxylic acids and esters of monoethylenically unsaturated carboxylic acids of polyoxy-C2-C4 alkyleneglycol mono-C1-C5 alkylether located at the tip of the pendant groups attached to the comb polymer.
The comb polymers of EP-A 725 044 contain monoethylenically unsaturated monocarboxylic acids and esters of monoethylenically unsaturated carboxylic acids with polyoxyethylene glycol mono-C1-C5 alkyl ethers located at the tip of pendant groups. The polymers are used as admixtures in hydraulically setting mixtures based on a mixture of cement and anhydrous gypsum.
The comb polymers of EP-A 799 807 contain mono-ethylenically unsaturated monocarboxylic acids and polyoxyalkylene glycol mono-C1-C22 alkylethers, located at the tip of pendant groups, and mono(meth)acrylic acid esters, the latter of which are obtained by a trans-esterification process.
The comb polymers of U.S. Pat. Nos. 5,728,207 and 5,840,114 contain cyclic anhydride groups and alkylpolyoxyalkylene ether amines.
Finally, comb polymers, as disclosed in World patent application No. WO 98/28353, contain a carbon backbone bearing alkyl-polyalkylene ether groups and carboxylate groups. These comb polymers are produced both by modification of carboxylate group-containing polymers with polyalkylene ethers and also by copolymerization of suitable monomers containing alkylpolyalkylene ether groups with ethylenically unsaturated carboxylic acids.
In US Patent Application 2008/0227890, Maeder et al. disclose the use of a comb polymer as a cement grinding additive, and in particular aqueous compositions containing poly(meth)acrylic acid derivatives in which some of the monomer units are esterified and some may be in the form of amide groups.
The present inventors, however, believe that novel compositions and methods are required for sustaining robustness of comb polymers that are used in mill grinding preparations of cementitious materials, so as to achieve workability and strength performance of the resultant ground cementitious materials.